T h e O b serv er ’s H a n d b o o k FOR 1940

PUBLISHED BY

The Royal Astronomical Society of Canada

C. A. CHANT, E d ito r F. S. HOGG, A s s is t a n t E d ito r DAVID DUNLAP OBSERVATORY

THIRTY-SECOND YEAR OF PUBLICATION

T O R O N TO 198 College Street Printed for the Society B y t h e U niversity of Toronto Press 1940 1940 CALENDAR 1940

JULIAN DAY CALENDAR, 1940 J. D. 2,420,000 plus the following: Jan. 1 9630 May 1...... 9751 Sept. 1...... 9874 Feb. 1 9661 June 1...... 9782 Oct. 1...... 9904 Mar. 1 9690 July 1...... 9812 Nov. 1 9935 Apr. 1 ...... 9721 Aug. 1...... 9843 Dec. 1...... 9965 The Julian Day commences at noon. Thus J.D. 2,429,630.0 = Jan. 1.5 G.C.T. T he O b serv er 's H a n d b o o k FOR 1940

PUBLISHED BY

T h e Royal Astronomical Society of Canada

C. A. CHANT, E dito r F. S. HOGG, A s s i s t a n t E ditor DAVID DUNLAP OBSERVATORY

TORONTO 198 C o l l e g e S t r e e t P r in t e d f o r t h e S o c ie t y B y t h e U n iv e r s it y o f T o r o n t o P r e s s 1940 CONTENTS

PAGE Preface - 3 Anniversaries and Festivals - - - 3

Symbols and Abbreviations - -- 4 The Constellations . . . - - 5

Miscellaneous Astronomical Data - - 6 Ephemeris of the Sun - - 7

Solar and Sidereal Time - - 8 Map of Standard Time Zones - - 9 Times of Sunrise and Sunset - - 10 The Planets for 1940 -- 17 Ephemerides of the Bright Asteroids, 1940 - -- 24 A Remarkable Grouping of Six Bright Planets - - 25 Eclipses, 1940 - -- 25 The Sky and Astronomical Phenomena Month by Month - 26 Phenomena of Jupiter’s Satellites - - 50 Phenomena of Saturn’s Satellites - - 52 Lunar Occultations ------52 Meteors or Shooting Stars - -- 54 Principal Elements of the Solar System - - 56 Satellites of the Solar System -- 57 Double and Multiple Stars, with a short list - - 58 Variable Stars, with a short list -- 60 Distances of the Stars, with a list of the Sun’s Neighbours - 62 The Brightest Stars, their magnitudes, types, proper motions, distances and radial velocities -- 64 Star Clusters and Nebulae, with Messier’s List - - 72 Four Circular Star Maps - -- 75 Times of Beginning and Ending of Twilight - - - 79 Transit of Mercury, 1940 Nov. 11-12 -- 80 Tables of Meteorological Data cover, p. iii

PRINTED IN CANADA PREFACE

The H a n d b o o k for 1940, which is the thirty-second issue, is arranged similarly to that of last year. The chief changes are: (1) The table of constellations has been re-set, giving the English as well as the Latin names; (2) The table of brightest stars has been completely revised by Dr. Harper and includes the latest available information; (3) An account of the transit of Mercury in 1940 is given. The small star maps at the back necessarily contain only a few objects. Four similar maps 9 inches in diameter are obtainable from the Director of University Extension, University of Toronto, for one cent each. Observers desiring fuller information are recommended to obtain Norton’s Star Atlas and Reference Handbook (Gall and Inglis, price 12s 6d; supplied also by Eastern Science Supply Co., Boston, Mass.). The sixth edition contains late information. For the preparation of the material in the volume Dr. F. S. Hogg, Assistant Editor, is largely responsible; but hearty thanks are due to all the staff of the David Dunlap Observatory for their assistance.

C. A. Chant. David Dunlap Observatory, Richmond Hill, Ont., November 1939.

ANNIVERSARIES AND FESTIVALS 1940 New Year’s D ay...... Mon. Jan. 1 St. John Baptist (Midsummer E piphany...... Sat. Jan. 6 Day)...... Mon. June 24 Septuagesima Sunday Jan. 21 Dominion D ay...... Mon. July 1 Quinquagesima (Shrove Birthday of Queen Elizabeth Sunday)...... Feb. 4 (1900)...... Sun. Aug. 4 Ash Wednesday...... Feb. 7 Labour D ay...... Mon. Sept. 2 Quadragesima (First St. Michael (Michaelmas Sunday in Lent) Feb. 11 D ay)...... Sun. Sept. 29 St. David...... Fri. Mar. 1 Hebrew New Year (Rosh St. Patrick...... Sun. Mar. 17 Hashanah)...... Thu. Oct. 3 Palm Sunday Mar. 17 All Saints’ D ay...... Fri. Nov. 1 Good Friday...... Mar. 22 Remembrance Day. . . .Mon. Nov. 11 Easter Sunday...... Mar. 24 St. Andrew...... Sat. Nov. 30 Annunciation (Lady First Sunday in Advent Dec. 1 Day)...... Mon. Mar. 25 Accession of King George VI St. George...... Tue. Apr. 23 (1936)...... Wed. Dec. 11 Rogation Sunday Apr. 28 Birthday of King George VI Ascension D ay...... Thu. May 2 (1895)...... Sat. Dec. 14 Pentecost (Whit Sunday) May 12 Christmas D ay . Wed. Dec. 25 Trinity Sunday May 19 Corpus Christi...... Thu. May 23 Empire Day (Victoria Day)...... Fri. May 24 Birthday of the Queen Mother, Thanksgiving Day, date set by Mary (1867)...... Sun. May 26 Proclamation SYMBOLS AND ABBREVIATIONS

SIGNS OF THE ZODIAC

SUN, MOON AND PLANETS

ASPECTS AND ABBREVIATIONS

THE GREEK ALPHABET

THE CONFIGURATIONS OF JUPITER’S SATELLITES In the Configurations of Jupiter’s Satellites (pages 27, 29, etc.), O represents the disc of the planet, d signifies that the satellite is on the disc, * signifies that the satellite is behind the disc or in the shadow. Configurations are for an inverting telescope. THE CONSTELLATIONS

L a t in a n d E n g l is h N a m e s w it h A bbreviations

Andromeda, Leo, Lion...... Leo Leon (Chained Maiden) .. .And Andr Leo Minor, Lesser Lion. .LMi LMin Antlia, Air Pum p...... Ant Antl Lepus, Hare...... Lep Leps Apus, Bird of Paradise. . Aps Apus Libra, Scales...... Lib Libr Aquarius, Water-bearer. . Aqr Aqar Lupus, Wolf...... Lup Lupi Aquila, Eagle...... Aql Aqil Lynx, L ynx...... Lyn Lync Ara, Altar...... Ara Arae Lyra, Lyre...... Lyr Lyra Aries, Ram ...... Ari Arie Mensa, Table (Mountain)Men Mens Auriga, (Charioteer). . . . Aur Auri Microscopium, Bootes, (Herdsman). . . . Boo Boot Microscope...... Mic Micr Caelum, Chisel...... Cae Cael Monoceros, Unicorn. . . . Mon Mono Camelopardalis, Giraffe. .Cam Caml Musca, F ly...... Mus Musc Cancer, Crab...... Cnc Canc Norma, Square...... Nor Norm Canes Venatici, Octans, Octant...... Oct Octn Hunting Dogs...... CVn CVen Ophiuchus, Canis Major, Greater Dog.CMa CMaj Serpent-bearer...... Oph Ophi Canis Minor, Lesser Dog.CMi CMin Orion, (Hunter)...... Ori Orio Capricornus, Sea-goat. . .Cap Capr Pavo, Peacock...... Pav Pavo Carina, Keel...... Car Cari Pegasus, (Winged Horse) Peg Pegs Cassiopeia, Perseus, (Champion).. . Per Pers (Lady in Chair)...... Cas Cass Phoenix, Phoenix...... Phe Phoe Centaurus, Centaur.... . Cen Cent Pictor, Painter...... Pic Pict Cepheus, (K ing)...... Cep Ceph Pisces, Fishes...... Psc Pisc Cetus, Whale...... Cet Ceti Piscis Australis, Chamaeleon, ChamaeleonCha. Cham Southern Fish...... PsA PscA Circinus, Compasses__ Cir Circ Puppis, Poop...... Pup Pupp Columba, Dove...... Col Colm Pyxis, Compass...... Pyx Pyxi Coma Berenices, Reticulum, Net...... Ret Reti Berenice's Hair...... Com Coma Sagitta, Arrow...... • Sge Sgte Corona Australis, Sagittarius, Archer...... Sgr Sgtr Southern Crown...... CrA CorA Scorpius, Scorpion...... Scr Scor Corona Borealis, Sculptor, Sculptor...... Scl Scul Northern Crown...... CrB CorB Scutum, Shield...... Sct Scut Corvus, Crow...... Crv Corv Serpens, Serpent...... Ser Serp Crater, Cup...... Crt Crat Sextans, Sextant...... Sex Sext Crux, (Southern) Cross. . Cru Cruc Taurus, Bull...... Tau Taur Cygnus, Swan...... Cyg Cygn Telescopium, Telescope. .Tel Tele Delphinus, Dolphin.... Del Dlph Triangulum, Triangle. . .Tri Tria Dorado, Swordfish...... Dor Dora Triangulum Australe, Draco, Dragon...... Dra Drac Southern Triangle---- TrA TrAu Equuleus, Little Horse.. .Equ Equl Tucana, Toucan...... Tuc Tucn Eridanus, River Eridanus. Eri Erid Ursa Major, Greater Bear.UMa UMaj Fornax, Furnace...... For Forn Ursa Minor, Lesser Bear.UMi UMin Gemini, Twins...... Gem Gemi Vela, Sails...... Vel Velr Grus, Crane...... Gru Grus Virgo, Virgin...... Vir Virg Hercules, Volans, Flying Fish.... Vol Voln (Kneeling Giant).... Her Herc Vulpecula, Fox...... Vul Vulp Horologium, Clock...... Hor Horo Hydra, Water-snake---- Hya Hyda The 4-letter abbreviations are in- Hydrus, Sea-serpent.... Hyi Hydi tended to be used in cases where a Indus, Indian...... Ind Indi maximum saving of space is not Lacerta, Lizard...... Lac Lacr necessary. MISCELLANEOUS ASTRONOMICAL DATA

U n i t s o f L e n g t h 1 Angstrom unit = 10-8 cm. 1 micron = 10-4 cm. 1 meter = 102 cm. = 3.28084 feet 1 kilometer = 105 cm. = 0.62137 miles 1 mile = 1.60935 X105 cm. = 1.60935 km. 1 astronomical unit = 1.49504 X1013 cm. = 92,897,416 miles 1 light year = 9.463 X1017 cm. = 5.880 X1012 miles =0.3069 parsecs 1 parsec = 30.84 X1017 cm. = 19.16 X1012 miles =3.259 l.y. 1 megaparsec = 30.84 X1023 cm. = 19.16X1018 miles =3.259 X106 l.y.

U n i t s o f T i m e Sidereal day = 23h 56m 04.09s of mean solar time Mean solar day = 24h 03m 56.56s of sidereal time Synodical month = 29d 12h 44m; sidereal month = 27d 07h 43m Tropical year (ordinary) = 365d 05h 48m 46s Sidereal year =365d 06h 09m 10s Eclipse year =346 d 14h 53m

T h e E a r t h Equatorial radius, a = 3963.35 miles; flattening, c = (a —b)/a =1/297.0 Polar radius, b = 3950.01 miles 1° of latitude = 69.057 —0.349 cos 2φ miles (at latitude φ) 1° of longitude = 69.232 cos φ—0.0584 cos 3φ miles Mass of earth = 6.6 X1021 tons; velocity of escape from O =6.94 miles/sec. E a r t h ’s O r b i t a l M o t i o n Solar parallax = 8."80; constant of aberration = 20."47 Annual general precession = 50."26; obliquity of ecliptic = 23° 26' 50" (1939) Orbital velocity = 18.5 miles/sec.; parabolic velocity at O = 26.2 miles/sec.

S o l a r M o t i o n Solar apex, R.A. 18h 04m; Dec. + 31° Solar velocity = 12.2 miles/sec.

T h e G a l a c t ic S y s t e m North pole of galactic plane R.A. 12h 40m, Dec. + 28° (1900) Centre, 325° galactic longitude, = R.A. 17h 24m, D ec. —30° Distance to centre = 10,000 parsecs; diameter = 30,000 parsecs. Rotational velocity (at sun) = 262 km./sec. Rotational period (at sun) = 2.2X108 years Mass = 2X1011 solar masses

E xtragalactic N e b u l a e Red shift =+530 km./sec./megaparsec=+101 miles /sec./million l.y.

R a d ia t io n C o n s t a n t s Velocity of light = 299,774 km./sec. = 186,271 miles/sec. Solar constant = 1.93 gram calories/square cm./minute Light ratio for one magnitude = 2.512; log ratio = 0.4000 Radiation from a star of zero apparent magnitude = 3 X10-6 meter candles Total energy emitted by a star of zero absolute magnitude = 5 X1025 horsepower

M iscellaneous Constant of gravitation, G = 6.670 X10- 8 c.g.s. units Mass of the electron, m = 9.035 X10-28 gm.; mass of the proton =1.662 X10-24 gm. Planck’s constant, h = 6.55 X10-27 erg. sec. Loschmidt’s number = 2.705 X1019 molecules/cu. cm. of gas at N.T.P. Absolute temperature = T° K =T°C+273° = 5/9 ( T° F + 4 5 9 °) 1 radian = 57°.2958 π = 3.141,592,653,6 = 3437'.75 No. of square degrees in the sky = 206,265" =41,253 1940 EPHEMERIS OF THE SUN AT Oh GREENWICH CIVIL TIME

To obtain local mean time, apply corr. to sundial to apparent or sundial tim e. 7 SOLAR AND SIDEREAL TIME In practical astronomy three different kinds of time are used, while in ordinary life we use a fourth. 1. Apparent Time—By apparent noon is meant the moment when the sun is on the meridian, and apparent time is measured by the distance in degrees that the sun is east or west of the meridian. Apparent time is given by the sun-dial. 2. Mean Time—The interval between apparent noon on two successive days is not constant, and a clock cannot be constructed to keep apparent time. For this reason mean time is used. The length of a mean day is the average of all the apparent days throughout the year. The real sun moves about the ecliptic in one year; an imaginary mean sun is considered as moving uniformly around the celestial equator in one year. The difference between the times that the real sun and the mean sun cross the meridian is the equation of time. Or, in general, Apparent Time—Mean Time = Equation of Time. This is the same as Correction to Sundial on page 7, with the sign reversed. 3. Sidereal Time—This is time as determined from the stars. It is sidereal noon when the Vernal Equinox or First of Aries is on the meridian. In accurate time-keeping the moment when a star is on the meridian is observed and the corresponding mean time is then computed with the assistance of the Nautical Almanac. When a telescope is mounted equatorially the position of a body in the sky is located by means of the sidereal time. 4. Standard Time—In everyday life we use still another kind of time. A moment’s thought will show that in general two places will not have the same mean time; indeed, difference in longitude between two places is determined from their difference in time. But in travelling it is very inconvenient to have the time varying from station to station. For the purpose of facilitating trans­ portation the system of Standard Time was introduced in 1883. Within a cer­ tain belt approximately 15° wide, all the clocks show the same time, and in passing from one belt to the next the hands of the clock are moved forward or backward one hour. In Canada we have six standard time belts, as follows;—60th meridian or Atlantic Time, 4h. slower than Greenwich; 75th meridian or Eastern Time, 5h.; 90th meridian or Central Time, 6h.; 105th meridian or Mountain Time, 7h.; 120th meridian or Pacific Time, 8h.; and 135th meridian or Yukon Time, 9h. slower than Greenwich. The boundaries of the time belts are shown on the map on page 9. MAP OF STANDARD TIME ZONES TIMES OF SUNRISE AND SUNSET In the tables on pages 11 to 16 are given the times of sunrise and sunset for places in latitudes 36°, 40°, 44°, 46°, 48°, 50° and 52°. The times are given in Local Mean Time, and in the table below are given corrections to change from Local Mean to Standard Time for the cities and towns named.

How the Tables are Constructed The time of sunrise and sunset at a given place, in local mean time, varies from day to day, and depends principally upon the declination of the sun. Varia­ tions in the equation of time, the apparent diameter of the sun and atmospheric refraction at the points of sunrise and sunset also affect the. final result. These quantities, as well as the solar declination, do not have precisely the same values on corresponding days from year to year, and so the table gives only approxi­ mately average values. The times are for the rising and setting of the upper limb of the sun, and are corrected for refraction. It must also be remembered that these times are computed for the sea horizon, which is only approximately realised on land surfaces, and is generally widely departed from in hilly and mountainous localities. The greater or less elevation of the point of view above the ground must also be considered, to get exact results.

The Standard Times for Any Station In order to find the time of sunrise and sunset for any place on any day, first from the list below find the approximate latitude of the place and the correction, in minutes, which follows the name. Then find in the monthly table the local time of sunrise and sunset for the proper latitude, on the desired day, and apply the correction to get the Standard Time.

34° min. 44° min. 46° min. 50° mi n . Los Angeles - 7 B rantford + 21 Glace Bay 0 Brandon +40 Guelph +21 Moncton + 19 K enora + 1 8 38° Halifax + 14 M ontreal - 6 Medicine Hat + 2 2 St. Louis + 1 Hamilton + 20 New Glasgow + 11 M oose Jaw + 2 San Francisco + 10 Kingston + 6 N o rth Bay + 18 Port. la Prairie +33 W ashington + 8 K itchener + 2 2 O ttaw a + 3 Regina - 2 M ilw aukee - 8 Parry Sound + 20 Trail - 9 40° Minneapolis + 13 Quebec - 1 5 V ancouver + 12 B altim ore + 6 Orillia + 18 St. John, N.B. + 2 4 Winnipeg +28 New York - 4 Oshawa + 15 Sault St. Marie + 3 7 Philadelphia + 1 Owen Sound + 2 4 Sherbrooke - 1 2 52° P ittsb u rg h + 2 0 Peterborough + 13 Sudbury + 2 4 C algary + 3 6 St. Catharines + 17 Sydney + 1 Saskatoon + 6 42° Stratfo rd + 2 4 Three Rivers - 1 0 Boston - 1 6 Toronto + 18 54° Buffalo + 15 Woodstock,Ont. +23 48° Edmonton +34 Chicago -10 Yarmouth + 24 Port Arthur +57 Prince Albert + 1 C leveland + 2 6 St. Jo h n ’s, Nfd. 0 Prince Rupert +41 D etro it - 2 8 46° Seattle + 9 London, Ont. +25 Charlottetown + 13 Timmins + 26 60° Windsor + 32 Fredericton +26 V ictoria + 13 D awson + 18

Example.—Find the time of sunrise at Owen Sound, also at Regina, on February 12. In the above list Owen Sound is under “44°”, and the correction is + 24 min. On page 11 the time of sunrise on February 12 for latitude 44° is 7.05; add 24 min. and we get 7.29 (Eastern Standard Time). Regina is under “50°”, and the correction is —2 min. From the table the time is 7.17 and sub­ tracting 2 min. we get the time of sunrise 7.15 (Mountain Standard Time). Latitude 36° Latitude 40° Latitude 44° Latitude 46° Latitude 48° Latitude 60° Latitude 52° DATE Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Latitude 36° Latitude 40° Latitude 44° Latitude 46° Latitude 48° Latitude 50° Latitude 52° Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Latitude 36° Latitude 40° Latitude 44° Latitude 46° Latitude 48° Latitude 50° Latitude 52° DATE Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Latitude 36° Latitude 40° Latitude 44° Latitude 46° Latitude 48° Latitude 50° Latitude 52° DATE Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Latitude 36° Latitude 40° Latitude 44° Latitude 46° Latitude 48° Latitude 50° Latitude 52° DATE Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Latitude 36° Latitude 40° Latitude 44° Latitude 46° Latitude 48° Latitude 50° Latitude 52° DATE Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset Sunrise Sunset THE PLANETS FOR 1940

By G. H. T idy

MERCURY Mercury is the nearest planet to the sun and completes one revolution in 88 days. The eccentricity of its orbit (.206) is very large compared with that of the other planets except Pluto, so that its distance from the sun varies from 28.5 million to 43.5 million miles. It is probably the smallest and least massive of the planets. Its period of rotation is the same as its period of revolution, so that the side nearest the sun is at a temperature of 670° F. and the other side is extremely cold. Since its orbit lies within that of the earth, the planet appears to move in the sky from one side of the sun to the other several times each year, greatest elongations (maximum separation from the sun) ranging from 18° to 28°. Since it is always fairly close to the ecliptic, the best time for observing it is at greatest eastern elongation in the spring and at greatest western elongation in the autumn, at which times the ecliptic is most nearly vertical. The dates of greatest elongation this year, together with the planet’s separation from the sun and magnitude, are as follows: East—Feb. 28, 18° 09', —0.6m (most favourable) ; June 24, 25° 18' + 0.7m; Oct. 20, 24° 30', +0.2m; and West—Apr. 12, 27° 40', +0.6m; Aug. 10, 18° 57' +0.4m; Nov. 28, 20° 11', —0.3m (most favourable). At these times the planet appears between 3" and 4" in diameter.

VENUS Venus, the second nearest planet to the sun, moves in a nearly circular orbit at a mean distance of 67 million miles from the sun, making one revolu­ tion in 225 days. The planet is almost the twin of the earth in size and mass, its diameter approximating 7,600 miles, and its average density being slightly less than that of the earth. A dense atmosphere surrounds the planet and prevents observation of its surface, so that its period of rotation is in doubt, though it seems likely to be about two weeks. Of all the major planets, Venus approaches the earth most closely and is the brightest object in the sky except the sun and moon. Like Mercury, it appears to oscillate from one side of the sun to the other in a period of 584 days, reaching a distance of about 47° from the latter at greatest elongations. On Jan. 1 it will be 2 hours east of the sun, and will move out to greatest eastern elongation on Apr. 17, when it will appear as an evening star of magnitude —3.9, 46° from the sun. It will then move back toward the sun, reaching inferior conjunction on June 26. Greatest western elongation will occur on Sept. 5, when it will be visible in the morning sky,again 46° from the sun, and magnitude —4.0. The semidiameter of the planet will be about 12" at greatest elongations and about 29" at inferior conjunction, the distances from the earth at these times being respectively 66 and 26.9 million miles. It will attain maximum brightness of —4.2 magnitudes in May and August.

MARS Mars is the farthest from the sun of the four inner planets. Its orbit is outside that of the earth, with a mean distance of 142 million miles. Due to the orbit’s eccentricity, the planet’s distance from the sun ranges between 128 and 154 million miles. It takes 687 days to complete one revolution, and the synodic period is 780 days, the longest in the solar system. One of the smallest of the major planets, it has a diameter of 4,200 miles. Since its thin atmosphere does not prevent observation of the surface detail, the period of rotation has been well determined, about 24h 37m. The surface temperature of the planet ranges from —90 °F. to +60 °F. Two faint moons, Phobos and Deimos, revolve in orbits close to the planet. When in opposition, the planet can approach the earth as close as 34,600,000 miles, but during 1940 it passes around the side of the sun farthest from the earth and is not in a favourable position for observation. In January it is about 5 hours east of the sun, which gradually overtakes it, and for several weeks before and after conjunction on Aug. 30, Mars is hidden by the sun’s light. It then appears as a morning star for the remain­ der of the year. Its semidiameter decreases from 3.7" in January to 1.8" in July.

THE ASTEROIDS

The g a p between the orbits of Mars and Jupiter is filled by very many small bodies, orbits of over 1,400 of which have been determined. Most of them are under 50 miles in diameter. Their orbits cover a fairly wide range in eccentricity and inclination to the ecliptic, and some of them pass very close to the earth. Several of the brightest asteroids approach magnitude 7 at opposition, and because of their changing brightness and rapid motion with respect to the stars, they are very interesting objects for observation. Ephemerides for some of the brightest of the asteroids are given on page 24 of this Handbook. Path of Mars among the Stars during 1940 In this and the following maps, the position of the planet is indicated for the first of each month. JUPITER

Jupiter, the largest and most massive of the planets, is except for the moon and Venus, the most conspicuous object in the night sky. At a mean distance of 483 million miles from the sun, it completes one revolution in 11.9 years. It has a very short period of rotation, about 10 hours. The spectroscope shows that the planet’s atmosphere contains ammonia and methane. The surface temperature is about —200 °F., showing that the planet radiates little heat of its own, contrary to former belief. Jupiter is an excellent object for observation, even with a small telescope. Much surface detail is visible, the flattening at the poles due to rotation

is quite evident, and four of the eleven moons discovered up to the present are easily observed. In January, Jupiter is five hours east of the sun in the constellation Pisces. The sun slowly overtakes it, conjunction occurring on Apr. 11. In June it is visible as a morning star 2 hours west of the sun, and western quadrature takes place on Aug. 6. That is, the planet is 90° from the sun on that date. The planet retrogrades from Sept. 4 to the end of the year. It is in opposition Nov. 2, when it appears as a bright star magnitude —2.4, on the meridian at midnight. Its distance from the earth and its semidiameter at opposition are respectively 370 million miles and 23". SATURN

Second only to Jupiter in size and mass, Saturn is the most remote of the six planets known to ancient astronomers. Saturn’s ring system makes the planet an unusually interesting object for telescopic observation. Since the rings are inclined at an angle of 27° to the plane of the planet’s orbit, they appear to open out twice in the 29½ years taken by the planet to complete one revolution. They were invisible in 1936 and will be opened out to a maximum in 1943, so that 1940 will be a good year for their observation. There are three important rings: the bright main ring, an outer one, and the inner crepe ring.

The planet has nine satellites of which the brightest is easily visible in a small telescope. At eastern quadrature Jan. 16, the planet will appear as a yellowish star of magnitude 0.6 in the constellation Pisces. After conjunction with the sun on April 24, Saturn will appear in the morning sky and will reach western quadrature on Aug. 6. Opposition occurs on Nov. 3, when the planet will be of magnitude 0.0. Its distance at that time will be 760 million miles, and its semidiameter will approximate 9". It is of interest to note that Saturn is occulted by the moon several times during 1940. These occultations are not visible in Canada. URANUS Uranus was discovered accidentally by Herschel in 1781. He at first mistook it for a comet, but later its true character was realized. The planet lies about 19 times as far from the sun as does the earth. A disk is perceptable only in large telescopes. Little has been learned about its surface markings due to its great distance which reduces the apparent semidiameter to about 1".8. However, the spectroscope has proven the existence of methane gas in the very cold atmosphere.

The period of revolution of this planet about the sun is 84 years, and its period of rotation is about 11 hours. Four satellites are known. Uranus may be seen during 1940 as a 6m star in Aries and Taurus. Eastern quadrature occurs on Feb. 7, and the planet is in a good position for observation. From March to June it is hidden by the sun. (Conjunction takes place on May 12.) After June it can be seen in the morning sky and it reaches western quadrature on Aug. 19. Opposition occurs on Nov. 16. Its distance is then about 1,720 million miles.

NEPTUNE The discovery of Neptune ranks as one of the greatest triumphs of mathe­ matical astronomy. It had long been noted that Uranus was not following exactly its predicted orbit, and from the irregularities Leverrier and Adams predicted independently the orbit and position of the hypothetical planet assumed to produce them. Neptune was discovered within one degree of the predicted position. Its distance from the sun is about 2,800 million miles and it requires 165 years to complete one revolution. It has one satellite. It is magnitude 8 and shows a disk 1".2 in diameter. During 1940 Neptune will be in the constellation Virgo. The planet will be in a favourable position for observation in the spring, since opposition will take place on Mar. 14, and it will pass eastern quadrature on June 13. Con­ junction will occur on Sept. 18, and the sun will interfere with observations a few months before and after that date. Western quadrature takes place on Dec. 19. The planet’s motion is direct from June 3 to Dec. 30.

PLUTO In March, 1930, Neptune lost its distinction as the outermost known planet of the solar system when Pluto was discovered at the Lowell Observatory as a result of a long systematic search initiated by Percival Lowell. Pluto’s distance from the sun is about 3,700 million miles and its period of revolution 248 years. Due to its great distance and lack of satellites we know little about its size and mass, other than that it seems similar to the terrestrial planets. It is about fifteenth magnitude, visible only in large tele­ scopes. Its position for dates near opposition (Jan. 23) is given below:

Date R.A. Dec. Date R.A. Dec. Jan. 4 8h 22m 09s +23° 22'.2 Ap r. 5 8h 15m 33s + 2 3 2 4 .7 Feb. 5. 8 19 11 + 2 3 3 4 .3 Nov. 27 8 31 04 + 2 3 1 3 .0 Mar. 4 8 16 55 +23 42.2 Dec. 29 8 29 07 +23° 45'.9 OPPOSITION EPHEMERIDES OF THE BRIGHTEST ASTEROIDS, 1940.

P r e p a r e d b y P r o f e s s o r G. S t r a c k e

1 Ceres 19 F ortuna Feb. 21...... 11h 35.6m +20° 52' Sept. 16...... 1h 15.0m+ 9° 9' 29...... 11 29.5+ 21 50 24...... 1 10.2 + 8 34 Mar. 8 11 22.6 + 22 39 Oct. 2 ...... 1 4.2 + 7 50 1 6 ...... 11 15.7 + 23 14 10 0 57.4 + 6 59 24 ...... 11 9.2 + 23 34 18 0 50.9 + 6 8 Apr. 1 11 3.8 + 23 37 26 0 45.1 + 5 22 Opp. Mar. 10 Mag. 7.0 Opp. Oct. 9 Mag. 8.8

2 Pallas 20 Massalia Dec. 19...... 7h 34.8m— 31° 3' Feb. 29...... 12h 12.8m— 4° 16' 2 7 7 30.0 - 31 24 Mar. 8 ...... 12 6.5 - 3 43 Jan. 4 7 23.9 - 31 15 16...... 11 59.3 - 2 59 1 2 7 17.2 - 30 29 24...... 11 52.0 - 2 9 2 0 7 10.7 - 29 5 Apr. 1 ...... 11 45.1 - 1 17 2 8 7 4.9 - 27 5 9 11 39.3 - 0 28 Opp. Jan. 10 Mag. 6.9 Opp. Mar. 19 Mag. 8.9

6 H ebe 132 Aethra Jan. 20...... 9h27.2m+ 12° 4' Dec. 27...... 8h 4.0m- 6° 13' 2 8 ...... 9 20.2 + 13 22 Jan. 4 ...... 7 57.0 - 10 15 Feb. 5 ...... 9 12.5 + 14 43 1 2 ...... 7 48.0 - 13 58 1 3 ...... 9 4.9 + 16 3 2 0 ...... 7 38.0 - 17 9 2 1...... 8 57.9 + 17 19 2 8 ...... 7 28.1 - 19 39 2 9 ...... 8 52.0 + 18 26 Feb. 5 ...... 7 19.5 - 21 24 Opp. Feb. 5 Mag. 8.9 Opp. Jan. 15 Mag. 9.2

9 Metis 192 Nausicaa Apr. 1 ...... 14h 1.8m— 5° 24' June 28...... 19h56.5m- 31° 19' 9 ...... 13 54.7 - 4 51 July 6 ...... 19 48.7 - 31 38 1 7 ...... 13 47.0 - 4 19 14...... 19 39.7 - 31 48 2 5 ...... 13 39.2 - 3 51 22...... 19 30.2 - 31 47 May.....3 ...... 13 31.9 - 3 29 30...... 19 21.1 - 31 35 11...... 13 25.8 - 3 15 Aug. 7 ...... 19 13.3 - 31 11 Opp. Apr. 18 Mag. 9.3 Opp. July 15 Mag. 8.7

16 Psyche 354 Eleonora Nov. 11...... 4h 53.0m+ 17° 47' Jan. 28...... 10h 11.5m+ 11° 35' 19...... 4 46.9 + 17 31 Feb. 5 10 6.6 + 13 14 27...... 4 39.8 + 17 16 1 3 10 0.8 + 14 58 Dec...... 5 ...... 4 32.4 + 17 3 2 1...... 9 54.7 + 16 42 1 3 . . . . 4 25.4 + 16 52 29 9 48.8 + 18 20 21...... 4 19.2 + 16 46 Mar. 8 9 43.7 + 19 47 Opp. Dec. 2 Mag. 9.1 Opp. Feb. 16 Mag. 9.3

These ephemerides have been made available through the kindness of Pro­ fessor Stracke and of Professor A. Kopff, the Director of the Astronomisches Rechen-Institut, of Berlin. Positions are for equinox of 1950. A REMARKABLE GROUPING OF SIX BRIGHT PLANETS

The western horizon, one-half hour after sunset, Feb. 28, 1940.

ECLIPSES FOR 1940

During 1940 there will be 2 eclipses, both of the sun. I. A n annular eclipse of the sun, April 7, visible in North America. The path of annular eclipse begins in the Pacific Ocean, crosses Southern California, and passes north of the Gulf of Mexico, entering the Atlantic off Florida. The partial phases will be visible throughout the continent except Alaska and the northern islands. On the Pacific Coast of Canada, the partial phase will begin about 20h and will end about 22h. In the Great Lakes region it will begin about 20h 30m and end about 23h. (Universal Time.) II. A total eclipse of the sun, October 1, invisible in Canada. The path of totality crosses the northern part of South America, the South Atlantic, and the southern tip of Africa. Length of totality on the east coast of South America and in South Africa is about 4m.

Circumstances of the Eclipse U. T. Longitude d h m from Green. Latitude Eclipse begins ...... 1 10 8 +64° 10' + 7° 58' Central eclipse begins 1 11 4 +78 30 + 2 41 Central eclipse ends 1 14 23 —53 47 —32 36 Eclipse ends ...... 1 15 19 —39 21 —27 20 25 THE SKY MONTH BY MONTH

B y P. M . M il l m a n

THE SKY FOR JANUARY, 1940

The times of transit are given in local mean time, 0h at midnight; to change to Standard Time, see p. 10. Estimates of altitude are for an observer in latitude 45° N. The Sun—During January the sun’s R.A. increases from 18h 41m to 20h 54m and its Decl. changes from 23° 07' S. to 17° 29' S. The equation of time (see p. 7) decreases from —2m 58s to —13m 29s. Owing to this rapid drop in value the time of mean noon appears, for the first ten days of the month, to remain at the same distance from sunrise, that is, the forenoons as indicated by our clocks are of the same length. For changes in the length of the day, see p. 11. The sun moves into the second winter sign of the zodiac, Aquarius, on the 20th of the month. The signs of the zodiac are all exactly 30° in length and now no longer correspond to the constellations of the same name. For example, the sign Aquarius is now situated among the stars of the constellation Capricornus. The earth is in perihelion, the point on its orbit nearest the sun, on January 2. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 18h 58m, Decl. 24° 04' S. and transits at 11.27. It is in superior conjunction with the sun on the 31st and not well placed for observation during January. Venus on the 15th is in R.A. 21h 54m, Decl. 14° 33' S. and transits at 14.21. It is a brilliant star in the western evening sky, being a little over 20° above the horizon at sunset and setting approximately 3 hours after the sun. Mars on the 15th is in R.A. Oh 28m, Decl. 2° 55' N. and transits at 16.53. It is a red first magnitude star on the meridian at sunset and setting approxi­ mately 6 hours after the sun. It is in conjunction with Jupiter on the 7th (see opposite page). Jupiter on the 15th is in R.A. Oh 13m, Decl. 0° 05' N. and transits at 16.37. It is on the meridian at sunset and sets about 6 hours after the sun. Conjunction with Mars takes place on the 7th. For the configurations of Jupiter’s satellites see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 1h 35m, Decl. 7° 16' N. and transits at 17.58. It is a pale yellow star in the evening sky, slightly brighter than the first magni­ tude. Saturn is in quadrature with the sun on the 15th and is in view for the first half of the night. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 03m, Decl. 16° 55' N. and transits at 19.26. Neptune on the 15th is in R.A. 11h 45m, Decl. 2° 56' N. and transits at 4.10. Pluto—For information in regard to this planet, see p. 23. ASTRONOMICAL PHENOMENA MONTH BY MONTH

B y R uth J. N orthcott

Config. JANUARY of Min. Jupiter’s 75th Meridian Civil Time of Sat. Algol 20h 15m The times of transit are given in local mean time, 0h at midnight; to change to Standard Time, see p. 10. Estimates of altitude are for an observer in latitude 45° N. The Sun—During February the sun’s R.A. increases from 20h 54m to 22h 47m and its Decl. changes from 17° 29' S. to 7° 43' S. The equation of time decreases from —13m 29s to a minimum of —14m 21s on the 12th and then increases to —12m 32s at the end of the month (see p. 7). For changes in the length of the day, see p. 11. The sun enters the sign Pisces, the third winter sign of the zodiac, on the 19th. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 22h 34m, Decl. 10° 20' S. and transits at 13.00. It reaches greatest elongation east of the sun in the evening sky on the 28th. At this time Mercury is 16° above the horizon at sunset and appears as a red star slightly brighter than zero magnitude. This is one of the most favourable times of the year for observing the planet in the evening sky. It sets about 1h 40m after the sun. Venus on the 15th is in R.A. 0h 13m, Decl. 0° 49' N. and transits at 14.38. It is slowly increasing its apparent distance from the sun in the western evening sky. On the evening of the 20th there is an interesting conjunction with Jupiter, the two planets being just over a degree apart at sunset (see opposite page). Mars on the 15th is in R.A. 1h 46m, Decl. 11° 23' N. and transits at 16.09. It is in the evening sky and visible in the south-west during the first part of the night. Mars is in conjunction with Saturn on the morning of the 13th and with the moon on the evening of the same date. At this time the moon, Mars and Saturn will be an interesting trio in the sky with Jupiter and Venus not far away. Jupiter on the 15th is in R.A. Oh 34m, Decl. 2° 24' N. and transits at 14.56. It is a bright star of magnitude —1.7, high in the south-west at sunset and setting nearly 4 hours after the sun. Conjunction with Venus takes place on the 20th. For the configurations of Jupiter’s satellites, see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 1h 42m, Decl. 8° 03' N. and transits at 16.03. It is high in the south at sunset and sets over 5 hours after the sun. Conjunction with Mars takes place on the 13th. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 03m, Decl. 16° 57' N. and transits at 17.24. Neptune on the 15th is in R.A. 11h 43m, Decl. 3° 10' N. and transits at 2.07. Pluto—For information in regard to this planet, see p. 23. NOTE.—During the last week in February and the first in March there will be a most unusual distribution of planets in the evening sky. The six brightest major planets will all be well placed for observation in the western evening sky and will lie along the ecliptic in a zone roughly 50° in length. Mer­ cury will be near the western horizon followed in order by Jupiter, Venus, Saturn, Mars, and Uranus. The five naked-eve planets will be within 40° of each other. For diagram see page 25. FEBRUARY Config. Min. of of Jupiter's 75th Meridian Civil Time Algol Sat. 19h 45m

Explanation of symbols and abbreviations on p. 4, of time on p. 8. The Sun—During March the sun’s R.A. increases from 22h 47m to 0h 41m and its Decl. changes from 7° 43' S. to 4° 24' N. The equation of time increases from —12m 32s to —4m 04s (see p. 7). For changes in the length of the day, see p. 12. The sun is at the vernal equinox and crosses the equator on its way north at 18h 24m G.C.T. March 20. This date marks the beginning of spring and day and night are approximately equal all over the world. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 23h 37m, Decl. 1° 24' N. and transits at 12.03. Mercury may be glimpsed for the first few days of the month near the western horizon just after sunset. It rapidly fades into the twilight glow, however, and reaches inferior conjunction with the sun on the 15th. Venus on the 15th is in R.A. 2h 18m, Decl. 15° 11' N. and transits at 14.48. The planet is noticeably increasing in brightness in the evening sky, being now of magnitude —3.7. It sets nearly 4 hours after the sun. It is in conjunction with the planet Saturn on the 8th. Mars on the 15th is in R.A. 3h 02m, Decl. 17° 58' N. and transits at 15.31. It is a red star, appearing high in the southwest at sunset and setting about five hours after the sun. Mars is slowly growing fainter as its distance from the earth increases. It is now of magnitude +1.5. Jupiter on the 15th is in R.A. 0h 58m, Decl. 4° 58' N. and transits at 13.25. It is steadily approaching the sun in the evening sky and now sets under two hours after that body. The magnitude is now —1.6. For the configurations of Jupiter’s satellites see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 1h 53m, Decl. 9° 09' N. and transits at 14.20. It is approaching the sun in the western evening sky and now sets about 3 hours after the sun. It is in conjunction with Venus on the 8th. Uranus on the 15th is in R.A. 3h 06m, Decl. 17° 11' N. and transits at 15.33. Neptune on the 15th is in R.A. 11h 40m, Decl. 3° 29' N. and transits at 0.10. Opposition to the sun is on the 14th. Pluto—For information in regard to this planet, see p. 23. NOTE.—During the last week in February and the first in March there will be the most unusual distribution of planets in the evening sky. The six brightest major planets will all be well placed for observation in the western evening sky and will lie along the ecliptic in a zone roughly 50° in length. Mercury will be near the western horizon, followed in order by Jupiter, Venus, Saturn, Mars, and Uranus. The five naked-eye planets will be within 40° of each other. For diagram, see page 25. Config. Min. of MARCH of Jupiter’s Algol Sat. 75th Meridian Civil Time 19h 30m The Sun—During April the sun's R.A. increases from 0h 41m to 2h 32m and its Decl. changes from 4° 24' N. to 14° 58' N. The equation of time increases from —4m 04s to +2m 54s (see p. 7). For changes in the length of the day, see p. 12. On the 21st the sun enters Taurus, the second spring sign of the zodiac. There is an annular eclipse of the sun on the 7th, visible in most of Canada and the United States as a partial eclipse. The central path lies across the extreme southern part of the United States. For details, see p. 25. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 23h 54m, Decl. 3° 12' S. and transits at 10.23. It is at western elongation in the morning sky on the 12th but not particularly well placed for observation since at best it rises under an hour before the sun and is only 8° above the horizon at sunrise. Venus on the 15th is in R.A. 4h 33m, Decl. 25° 18' N. and transits at 15.02. It reaches its greatest elongation east of the sun on the 17th and is a brilliant yellow-white star of magnitude —4, setting 4 hours after the sun. It appears high in the west almost directly the sun has dropped below the horizon. Mars on the 15th is in R.A. 4h 27m, Decl. 22° 44' N. and transits at 14.54. It is visible in the western evening sky just to the north of Aldebaran, the two objects appearing as a pair of red stars. Jupiter on the 15th is in R.A. 1h 25m, Decl. 7° 48' N. and transits at 11.51. It is in conjunction with the sun on the 11th and too near that body for observa­ tion during April. Saturn on the 15th is in R.A. 2h 07m, Decl. 10° 29' N. and transits at 12.32. It is too near the sun to be well observed during April. Conjunction with the sun is on the 24th, at which time the planet enters the morning sky. Uranus on the 15th is in R.A. 3h 12m, Decl. 17° 35' N. and transits at 13.37. Neptune on the 15th is in R.A. 11h 38m, Decl. 3° 48' N. and transits at 22.01. Pluto—For information in regard to this planet, see p. 23. APRIL Min. of 75th Meridian Civil Time Algol

Explanation of symbols and abbreviations on p. 4, of time on p. 8. Jupiter being near the Sun, phenomena of the satellites are not given from March 27 to May 26. The Sun—During May the sun’s R.A. increases from 2h 32m to 4h 35m and its Decl. changes from 14° 58' N. to 22° 0' N. The equation of time increases from +2m 54s at the beginning of the month to a maximum of +3m 45s on the 14th and then drops to +2m 24s at the end of the month (see p. 7). For changes in the length of the day, see p. 13. On May 21 the sun enters Gemini, the third spring sign of the zodiac. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 2h 55m, Decl. 15° 49' N. and transits at 11.27. It is in superior conjunction with the sun on the 21st and too near the sun to be observed during May. Venus on the 15th is in R.A. 6h 26m, Decl. 27° 04' N. and transits at 14.55. It is slowly approaching the sun in the evening sky and at the same time increasing in brilliance. Maximum brightness of Venus is on May 20, at which time it is a star of magnitude —4.2 and may just be seen with the naked eye in broad daylight if one knows the exact spot in which to look. One way to see Venus in the daytime is to locate the direction due south, which will mark the meridian. Venus will transit this line at the given time and at an altitude h = 90—φ+ δ where φ is observer’s latitude and δ is Decl. of Venus. Mars on the 15th is in R.A. 5h 53m, Decl. 24° 32' N. and transits at 14.21. It is about 28° above the horizon at sunset and just north of the west point. Mars sets about 3 hours after the sun. Jupiter on the 15th is in R.A. 1h 52m, Decl. 10° 22' N. and transits at 10.20. It is close to the sun in the morning sky and not well placed for observation this month. For the configurations of Jupiter’s satellites, see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 2h 21m, Decl. 11° 45' N. and transits at 10.49. It is too near the sun in the morning sky for observation. Uranus on the 15th is in R.A. 3h 19m, Decl. 18° 02' N. and transits at 11.46. Neptune on the 15th is in R.A. 11h 36m, Decl. 3° 59' N. and transits at 20.01. Pluto—For information in regard to this planet, see p. 23. Config. MAY of Min. Jupiter's of Sat. 75th Meridian Civil Time Algol 4h 30m

Explanation of symbols and abbreviations on p. 4, of time on p. 8. Jupiter being near the Sun, phenomena of the satellites are not given from March 27 to May 26. The Sun—During June the sun’s R.A. increases from 4h 35m to 6h 39m and its Decl. changes from 22° 0' N. to a maximum of 23° 26'.6 N. on June 21 and then decreases to 23° 08' N. The equation of time decreases from +2m 24s to —3m 34s (see p. 7). The sun is at the summer solstice at 13h 37m G.C.T. June 21, at which time it is furthest north of the equator, and days are longest in the northern hemisphere. For changes in the length of the day, see p. 13. It will be noticed that the duration of daylight changes little during the last half of June. The local mean time of sunset is almost constant owing to the decrease in the equation of time. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 7h 13m, Decl. 24° 11' N. and transits at 13.42. During the month the planet is slowly separating from the sun in the evening sky and reaches eastern elongation on the 24th. At this time Mercury sets about an hour and a half after the sun and is 16° above the horizon at sunset. It may be seen for about a week before and after elongation, a red star of magnitude + 0 .7. There is a close conjunction with Mars on the 16th (see opposite page). Venus on the 15th is in R.A. 6h 50m, Decl. 22° 56' N. and transits at 13.13. It is rapidly approaching the sun in the evening sky. The planet reaches a stationary point on June 4 and commences to retrograde, or move west, at this time. There is a close conjunction between Mars and Venus on the 7th, visible best on the evening of the 6th. Venus is in inferior conjunction with the sun on the 26th and passes into the morning sky at this time. Mars on the 15th is in R.A. 7h 20m, Decl. 23° 21' N. and transits at 13.46. It is gradually fading into the evening twilight and is not particularly well placed for observation, setting under two hours after the sun. Conjunction with Venus takes place on the 7th. Jupiter on the 15th is in R.A. 2h 18m, Decl. 12° 37' N. and transits at 8.43. Its distance from the sun in the morning sky is now rapidly increasing. It rises two and a half hours before the sun and is due east and 25° above the horizon at sunrise. The moon will be observed near Jupiter on the morning of the 30th from the western part of the continent. For the configurations of Jupiter’s satellites, see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 2h 35m, Decl. 12° 51' N. and transits at 9.01. It rises just over two hours before the sun in the morning sky. Uranus on the 15th is in R.A. 3h 26m, Decl. 18° 29' N. and transits at 9.51. Neptune on the 15th is in R.A. 11h 35m, Decl. 4° 00' N. and transits at 17.59. Pluto—For information in regard to this planet, see p. 23. Config. JUNE of Min. Jupiter’s of Sat. 75th Meridian Civil Time Algol 4h 00m

Explanation of symbols and abbreviations on p. 4, of time on p. 8. 37 The Sun—During July the sun’s R.A. increases from 6h 39m to 8h 44m and its Decl. changes from 23° 08' N. to 18° 07' N. The equation of time drops from —3m 34s to a minimum of —6m 22s on the 26th and then rises to —6m 13s at the end of the month (see p. 7). For changes in the length of the day, see p. 14. The sun enters Leo, the second summer sign of the zodiac, on the 22nd. The earth is in aphelion, the point on its orbit furthest from the sun, on the 4th. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 8h 20m, Decl. 15° 15' N. and transits at 12.45. It is in inferior conjunction on the 22nd and is too near the sun to be observed during July. Venus on the 15th is in R.A. 5h 48m, Decl. 17° 59' N. and transits at 10.14. It is gradually separating from the sun in the morning sky and by the 15th is rising an hour and a half before the sun and appears 16° above the eastern horizon at sunrise. There is an occultation of Venus by the moon on July 31. This is visible in Western Canada (see p. 53). Towards the end of the month Venus is once more approaching its greatest brilliance, and, if located before sunrise, may be followed on into the daylight sky. It will be particularly easy to locate late on the 31st since at this time it will be between the moon and the sun, and quite near the former. Mars on the 15th is in R.A. 8h 40m, Decl. 19° 34' N. and transits at 13.08. During July Mars is too near the sun in the western evening sky to be well observed. Jupiter on the 15th is in R.A. 2h 38m, Decl. 14° 13' N. and transits at 7.06. It is slowly brightening in the morning sky, being now of magnitude —2. It is in view for most of the last half of the night. For the configurations of Jupiter’s satellites, see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 2h 46m, Decl. 13° 35' N. and transits at 7.13. It is steadily separating from the sun in the morning sky and appears as a pale yellow star of magnitude +0.5. On the morning of the 28th it will be observed close to the moon. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 32m, Decl. 18° 49' N. and transits at 7.59. Neptune on the 15th is in R.A. 11h 37m, Decl. 3° 49' N. and transits at 16.03. Pluto—For information in regard to this planet, see p. 23. Config. JULY of Min. Jupiter’s of Sat. 75th Meridian Civil Time Algol 3h 15m The Sun—During August the sun’s R.A. increases from 8h 44m to 10h 40m and its Decl. changes from 18° 07' N. to 8° 25' N. The equation of time increases from —6m 13s to — 0m 06s (see p. 7). For changes in the length of the day, see p. 14. The sun enters Virgo, the third summer sign of the zodiac, on the 23rd. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 8h 25m, Decl. 19° 05' N. and transits at 10.54. It is in the morning sky and reaches greatest elongation west of the sun on the 10th. It rises barely an hour before the sun, however, and is only about 9° above the horizon at sunrise, so is not particularly well placed for observation. Venus on the 15th is in R.A. 6h 35m, Decl. 18° 39' N. and transits at 9.02. It is a very bright star in the morning sky, rising several hours before the sun. Greatest brilliance occurs on the 2nd, at which time Venus is of magnitude —4.2, It may be followed on into the daylight sky during the first part of the month. Mars on the 15th is in R.A. 9h 59m, Decl. 13° 34' N. and transits at 12.24. It is rapidly approaching the sun in the evening sky. Conjunction takes place on the 30th at which time Mars enters the morning sky. Jupiter on the 15th is in R.A. 2h 52m, Decl. 15° 08' N. and transits at 5.17. It is in quadrature on the 6th and rises 7 hours before the sun, being on the meridian at sunrise. Conjunction with Saturn takes place on the 15th (see opposite page). For the configurations of Jupiter’s satellites, see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 2h 52m, Decl. 13° 54' N. and transits at 5.17. It rises over 4 hours before the sun and is high in the south-east at sunrise. It is in quadrature with the sun on the 6th. On the 27th Saturn reaches a stationary point on its orbit and starts to retrograde, or move westward, among the stars. In a telescope the rings appear fairly well open and are seen from the south side. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 35m, Decl. 19° 00' N. and transits at 6.00. Neptune on the 15th is in R.A. 11h 40m, Decl. 3° 28' N. and transits at 14.04. Pluto—For information in regard to this planet, see p. 23. Config. AUGUST of Min. Jupiter’s of Sat. 75th Meridian Civil Time Algol 2h 45m

Explanation of symbols and abbreviations on p. 4, of time on p. 8. 41 The times of transit are given in local mean time, 0h at midnight; to change to Standard Time, see p. 10. Estimates of altitude are for an observer in latitude 45° N. The Sun—During September the sun’s R.A. increases from 10h 40m to 12h 28m and its Decl. changes from 8° 25' N. to 3° 02' S. The equation of time increases from — 0m 06s to +10m 10s (see p. 7). For changes in the length of the day, see p. 15. The sun enters Libra and is at the autumnal equinox at 4h 46m G.C.T. on Sept. 23. This is the beginning of autumn and day and night are approximately equal all over the world. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 12h 05m, Decl. 0° 28' N. and transits at 12.31. It is in superior conjunction with the sun on the 4th and too near that body to be observed during September. Venus on the 15th is in R.A. 8h 33m, Decl. 16° 59' N. and transits at 8.58. The planet is very prominent in the morning sky and reaches greatest apparent elongation west of the sun on the 5th. At this time Venus rises 4 hours before the sun and is 40° above the horizon at sunrise. It is a very brilliant yellow star. Mars on the 15th is in R.A. 11h 13m, Decl. 6° 11' N. and transits at 11.37. It is in the morning sky and too near the sun for observation. Jupiter on the 15th is in R.A. 2h 54m, Decl. 15° 11' N. and transits at 3.17. It is fast moving into the evening sky and now rises well before midnight. Jupiter reaches a stationary point in its orbit and starts to retrograde, or move west among the stars, on the 4th. For the configurations of Jupiter’s satellites, see opposite page, and for their eclipses, etc., see p. 50. Saturn on the 15th is in R.A. 2h 51m, Decl. 13° 44' N. and transits at 3.15. It is in view for the greater part of the night, rising about 2 hours after sunset. The stellar magnitude has now increased to +0.3. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 35m, Decl. 19° 00' N. and transits at 3.59. Neptune on the 15th is in R.A. 11h 44m, Decl. 3° 02' N. and transits at 12.06. Pluto—For information in regard to this planet, see p. 23. Config. SEPTEMBER of Min. Jupiter’s of Sat. 75th Meridian Civil Time Algol 2h 00m

Explanation of symbols and abbreviations on p. 4, of time on p. 8. 43 The Sun—During October the sun’s R.A. increases from 12h 28m to 14h 24m and its Decl. changes from 3° 02' S. to 14° 19' S. The equation of time increases from +10m 10s to +16m 20s (see p. 7). For changes in the length of the day, see p. 15. On October 23rd the sun enters Scorpio, the second autumnal sign of the zodiac. There is a total eclipse of the sun on October 1st, invisible in North America. For details, see p. 25. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 14h 48m, Decl. 18° 47' S. and transits at 13.15. It is in the evening sky and is at greatest eastern elongation on the 20th. This is not a favourable elongation for observing the planet since at best it is only 6° above the south-western horizon at sunset and sets about forty minutes after the sun. Venus on the 15th is in R.A. 10h 44m, Decl. 8° 40' N. and transits at 9.11. It is slowly approaching the sun in the morning sky and its brightness is decreas­ ing. The magnitude is now —3.7, a drop of half a magnitude from its greatest brilliancy, which occurred in August. Mars on the 15th is in R.A. 12h 24m, Decl. 1° 33' S. and transits at 10.49. It is near the sun in the morning sky, rising an hour and a half before the sun and being 15° above the horizon at sunrise. Jupiter on the 15th is in R.A. 2h 44m, Decl. 14° 26' N. and transits at 1.10. It is now in view for almost all the night, having increased in brightness to magnitude —2.4 and rising about an hour after sunset. Conjunction with Saturn takes place on the 11th. For the configurations of Jupiter’s satellites see oppo­ site page, and for their eclipses, etc., see p. 51. Saturn on the 15th is in R.A. 2h 45m, Decl. 13° 11' N. and transits at 1.10. It is in view most of the night as a pale yellow star of magnitude +0.1, Early on the evening of the 17th it will be observed very near the moon. Saturn is actually occulted 8 times during the last 7 months of the year, but none of these occultations is visible in Canada. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 32m, Decl. 18° 51' N. and transits at 1.58. Neptune on the 15th is in R.A. 11h 48 m, Decl. 2° 37' N. and transits at 10.12. Pluto—For information in regard to this planet, see p. 23. Config. OCTOBER of Min. Jupiter's of Sat. 75th Meridian Civil Time Algol 1h 15m The Sun—During November the sun’s R.A. increases from 14h 24m to 16h 28m and its Decl. changes from 14° 19' S. to 21° 45' S. The equation of time increases from +16m 20s to a maximum of + 1 6m 22s on the 3rd and then drops to +11m 04s at the end of the month (see p. 7). For changes in the length of the day, see p. 16. On the 22nd the sun enters Sagittarius, the third autumnal sign of the zodiac. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 14h 54m, Decl. 15° 29' S. and transits at 11.13. The planet is in inferior conjunction and transits the sun on November 11th (see p. 80). At this time it moves into the morning sky and gradually separates from the sun, reaching its greatest apparent distance west of that body on the 28th. The two weeks centred on this date provide a good opportunity for observing Mercury. It will appear as a red star of magnitude —0.2, 17° above the horizon at sunrise on the 28th. On this date it rises about 2 hours before the sun. Venus on the 15th is in R.A. 13h 02m, Decl. 4° 35' S. and transits at 9.26. It is a brilliant star of magnitude —3.5 rising about 3 hours before the sun in the morning sky. Mars on the 15th is in R.A. 13h 38m, Decl. 9° 25' S. and transits at 10.02. It is a red star of 2nd magnitude, rising a little over 2 hours before the sun in the morning sky. Jupiter on the 15th is in R.A. 2h 28m, Decl. 13° 12' N. and transits at 22.48. It is in opposition to the sun on the 2nd, being in view all night at this time. It will be fairly near the moon early on the evening of November 13. For the configurations of Jupiter’s satellites see opposite page, and for their eclipses, etc., see p. 51. Saturn on the 15th is in R.A.2h 35m, Decl. 12° 27' N. and transits at 22.55. It is in opposition to the sun on the 3rd and at this time is in view all night, rising at sunset. The stellar magnitude is just 0.0. A very close conjunction with the moon will be visible in Canada and the United States on the evening of the 13th. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 28m, Decl. 18° 34' N. and transits at 23.47. Opposition to the sun is on the 16th. Neptune on the 15th is in R.A. 11h 51m, Decl. 2° 16' N. and transits at 8.14. Pluto—For information in regard to this planet, see p. 23. Config. NOVEMBER of Min. Jupiter’s of Sat. 75th Meridian Civil Time Algol 23h 45m The times of transit are given in local mean time, 0h at midnight; to change to Standard Time, see p. 10. Estimates of altitude are for an observer in latitude 45° N. The Sun—During December the sun’s R.A. increases from 16h 28m to 18h 44m and its Decl. changes from 21° 45' S. to a minimum of 23° 26'.7 S. on December 21st and then rises at the end of the month to 23° 03' S. The equation of time decreases from 11m 04s to —3m 21s (see p. 7). At 23h 55m G.C.T. December 21th the sun is at the winter solstice and enters Capricornus, the first winter sign of the zodiac. The length of daylight in the northern hemisphere is at a minimum, changing very slightly for several days, see p. 16. The Moon—For its phases, perigee and apogee times and distances, and its conjunctions with the planets, see opposite page. Mercury on the 15th is in R.A. 16h 25m, Decl. 21° 02' S. and transits at 10.53. For the first few days of the month the planet will still be visible in the morning sky (see p. 46). It then approaches the sun too closely to be observed during the remainder of December. Venus on the 15th is in R.S. 15h 23m, Decl. 16° 54' S. and transits at 9.50. It is approaching the sun in the morning sky and rises two and a half hours before sunrise. The magnitude is now —3.4 and it is just over 20° above the horizon at sunrise. Mars on the 15th is in R.A. 14h 55m, Decl. 16° 08' S. and transits at 9.20. It is slowly separating from the sun in the morning sky. It now rises over 3 hours before the sun and is 25° above the horizon at sunrise. Conjunction with Venus takes place on the 2nd (see opposite page). Jupiter on the 15th is in R.A. 2h 17m, Decl. 12° 22' N. and transits at 20.38. It reaches a stationary point on its orbit on the 31st and at this time commences to move eastward again among the stars. It is still a brilliant object in the night sky, setting just before sunrise. A close conjunction with the moon will take place early on the evening of the 10th (see opposite page). For the con­ figurations of Jupiter’s satellites see opposite page, and for their eclipses, etc., see p. 51. Saturn on the 15th is in R.A. 2h 28m, Decl. 11° 55' N. and transits at 20.49. It is well placed for observation, rising shortly before sunset and remaining in view most of the night. A very close conjunction with the moon will be visible on the night of December 10-11. For the elongations of Saturn’s satellites, etc., see p. 52. Uranus on the 15th is in R.A. 3h 23m, Decl. 18° 16' N. and transits at 21.44. Neptune on the 15th is in R.A. 11h 53m, Decl. 2° 05' N. and transits at 6.17. Pluto—For information in regard to this planet, see p. 23. Config. DECEMBER of Min. Jupiter's of Sat. 75th Meridian Civil Time Algol 22h 30m

OCTOBER NOVEMBER— Cont.

E—eclipse, O—occultation, T— transit, S—shadow, D— disappearance, R—reappearance, I—ingress, e—egress. The Roman numerals denote the satellites. 75th Meridian Civil Time. (For other times see p. 8). LUNAR OCCULTATIONS

Prepared by J. F. H eard When the moon passes between the observer and a star that star is said to be occulted by the moon and the phenomenon is known as a lunar occultation. The passage of the star behind the east limb of the moon is called the immersion and its appearance from behind the west limb the emersion. As in the case of eclipses, the times of immersion and emersion and the duration of the occultation are different for different places on the earth’s surface. The tables given below, adapted from the 1940 Nautical Almanac, give the times of immersion or emersion or both for occultations of stars brighter than magnitude 5.0 visible at Toronto and at Montreal and also at Vancouver and Calgary, at night. Occultations of stars fainter than magnitude 4.5 are excluded for 24 hours before and after Full Moon. Emersions at the bright limb of the moon are given only in the case of stars brighter than magnitude 3.5, and immersions at the bright limb only in the case of stars brighter than magnitude 4.5; so that most of the phenomena listed take place at the dark limb. The terms a and b are for deter­ mining corrections to the times of the phenomena for stations within 300 miles of Toronto or Montreal in the first table, and within 300 miles of Vancouver or Calgary, in the second table. Thus if λ0, φ0, be the longitude and latitude of the standard station and λ, φ, the longitude and latitude of the neighbouring station then for the neighbouring station we have— Standard Time of phenomenon = Standard Time of phenomenon at the standard station +a(λ—λ0)+b(φ —φ0) where λ—λ0 and φ—φ0 are expressed in degrees. The quantity P in the table is the position angle of the point of contact on the moon’s disc reckoned from the north point towards the east. Attention is called to a day-time occultation of Venus visible in Western Canada on July 31.

LUNAR OCCULTATIONS VISIBLE AT TORONTO AND MONTREAL. 1940

*Immersion or Emersion.

LUNAR OCCULTATIONS VISIBLE AT VANCOUVER AND CALGARY 1940

*Immersion or Emersion. METEORS OR SHOOTING STARS

By P eter M . M il l m a n Meteors are small fragmentary particles of iron or stone, the debris of space, which, on entering the earth’s atmosphere at high velocity, ignite and are in general completely vaporized. On a clear moonless night a single observer should see on the average about 7 meteors per hour during the first six months of the year and approximately twice this number during the second half of the year. The above figures are averages over the whole night, however, and it should be noted that meteors are considerably more numerous during the second half of the night at which time the observer is on the preceding hemisphere of the earth in its journey around the sun. In addition to the so-called sporadic meteors there are well-marked groups of meteors which travel in elliptical orbits about the sun and appear at certain seasons of the year. The meteors of any one group, or shower, move along parallel paths and hence, owing to the laws of perspective, seem to radiate from a point in the sky known as the radiant. The shower is usually named after the constellation in which the radiant is located. The following table lists the chief meteoric showers of the year. The material was collected from different sources, including the publications of Denning and Olivier. The Chief Annual Meteor Showers for the Northern Hemisphere. Approx. Radiant Hourly Maximum No. (all Duration Abbre­ Shower a 5 D ate meteors) (in days) viation Quadrantids 232° +52° Jan. 3 20 4 Q Lyrids 280 + 37 Apr. 21 10 4 Y Eta Aquarids 336 - 1 M ay 4 10 8 E Delta Aquarids 340 -17 July 28 20 3 D Perseids 47 + 5 7 Aug. 12 50 25 P Orionids 96 + 15 Oct. 22 20 14 O Leonids 152 +22 Nov.16 20 14 L Geminids 110 + 3 3 Dec. 12 30 14 G The date of maximum given above applies to either morning or evening and is approximate only, as local irregularities in the showers in addition to the effect of leap year may shift it by a day or more. With the exception of the Geminids, all the showers listed are most active well after midnight. It should be noted that large numbers of meteors appeared on June 28, 1916, and on Oct. 9, 1933, and there is the possibility of a return of these showers. A meteor observer should make as complete a record as he can with efficiency. The most important information to note includes the number of meteors per hour, their magnitudes and positions in the sky, evidences of enduring trains and, where several stations are co-operating, the exact time of the appearance of each meteor. Magnitudes of meteors are generally deter­ mined by comparison with stars and the positions of meteor trails may most conveniently be recorded by plotting them as straight lines on gnomonic star maps. The observer should also make sure that the record sheet contains his name, the exact place of observation, the night when the observations were made given as a double date (e.g. the evening of May 4 or the morning of May 5 would be recorded as May 4-5), and finally, a note on the weather conditions. The first curve shown in the figure below gives the expected hourly rate of meteors for a single observer at different times of the year. It has been drawn from data published by Denning, Olivier, and Hoffmeister. This curve varies somewhat from year to year. The corresponding curve for the southern hemisphere, which is not plotted, lacks the high maximum at P, has its highest maxima at E and D, and best general rates from April through July. The second curve gives the number of meteor photographs found on all Harvard patrol plates up to Oct. 15, 1936, for each five-day interval throughout the year, taken from a catalogue of meteor photographs published by Miss Hoffleit. Since these plates were exposed on a uniform system the curve gives some indication of the favourable periods for meteor photography. The high photographic efficiency of the Geminid shower is a marked feature.

Of recent years the study of meteors has become increasingly important both because of its cosmic significance and because of its close association with studies of the upper atmosphere. The amateur who does not possess a telescope can render more real assistance in this field than in any other. In particular, all observations of very bright meteors or fireballs should be reported imme­ diately in full. Maps and instructions for meteor observations may be secured from the writer at the Dunlap Observatory, Richmond Hill, Ont., the Canadian headquarters for the collection of meteor data. For more complete instructions concerning the visual observation of meteors see the J o u r n a l of the Royal Astronomical Society of Canada, vol. 31, p. 255, 1937; and for meteor photography volume 31, p. 295, 1937. PRINCIPAL ELEMENTS OF THE SOLAR SYSTEM

ORBITAL ELEMENTS (Jan. 1, 0h, 1938)

PHYSICAL ELEMENTS S a t e l l it e o f t h e E a r t h Moon

S a t e l l it e s o f M a r s Phobos Hall, 1877 Deimos Hall, 1877

S a t e l l it e s o f J u p it e r V Barnard, 1892 Io Galileo, 1610 Europa Galileo, 1610 Ganymede Galileo, 1610 Callisto Galileo, 1610 VI Perrine, 1904 VII Perrine, 1905 X Nicholson, 1938 XI Nicholson, 1938 VIII Melotte, 1908 IX Nicholson, 1914

S a t e l l it e s o f S a t u r n Mimas W. Herschel, 1789 Enceladus W. Herschel, 1789 Tethys G. Cassini, 1684 Dione G. Cassini, 1684 Rhea G. Cassini, 1672 Titan Huygens, 1655 Hyperion G. B ond,1848 Iapetus G. Cassini, 1671 Phoebe W. Pickering, 1898

S a t e l l it e s o f U r a n u s Ariel Lassell, 1851 Umbriel Lassell, 1851 Titania W. Herschel, 1787 -Oberon W. Herschel, 1787

S a t e l l it e o f N e p t u n e (Triton) Lassell, 1846

*As seen from the sun. DOUBLE AND MULTIPLE STARS

By F r a n k S. H ogg

A number of the stars which appear as single to the unaided eye may be separated into two or more components by field glasses or a small telescope. Such objects are spoken of as double or multiple stars. With larger telescopes pairs which are still closer together may be resolved, and it is found that, up to the limits of modern telescopes, over ten per cent. of all the stars down to the ninth magnitude are members of double stars. The possibility of resolving a double star of any given separation depends on the diameter of the telescope objective. Dawes' simple formula for this relation is d"=4.5/A, where d is the separation, in seconds of arc, of a double star that can be just resolved, and A is the diameter of the objective in inches. Thus a one-inch telescope should resolve a double star with a distance of 4".5 between its components, while a ten-inch telescope should resolve a pair 0".45 apart. It should be noted that this applies only to stars of comparable bright­ ness. If one star is markedly brighter than its companion, the glare from the brighter makes it impossible to separate stars as close as the formula indicates. This formula may be applied to the observation of double stars to test the quality of the seeing and telescope. It is obvious that a star may appear double in one of two ways. If the com­ ponents are at quite different distances from the observer, and merely appear close together in the sky the stars form an optical double. If, however, they are in the same region of space, and have common proper motion, or orbital motion about one another, they form a physical double. An examination of the proba­ bility of stars being situated sufficiently close together in the sky to appear as double shows immediately that almost all double stars must be physical rather than optical. Double stars which show orbital motion are of great astrophysical importance, in that a careful determination of their elliptical orbits and parallaxes furnishes a measure of the gravitational attraction between the two components, and hence the mass of the system. In the case of many unresolvable close doubles, the orbital motion may be determined by means of the spectroscope. In still other doubles, the observer is situated in the orbital plane of the binary, and the orbital motion is shown by the fluctuations in light due to the periodic eclipsing of the components. Such doubles are designated as spectroscopic binaries and eclipsing variables. The accompanying table provides a list of double stars, selected on account of their brightness, suitability for small telescopes, or particular astrophysical interest. The data are taken chiefly from Aitken’s New General Catalogue of Double Stars, and from the Yale Catalogue of Bright Stars. Successive columns give the star, its 1900 equatorial coordinates, the magnitudes and spectral classes of its components, their separation, in seconds of arc, and the approximate distance of the double star in light years. The last column gives, for binary stars of well determined orbits, the period in years, and the mean separation of the components in astronomical units. For stars sufficiently bright to show colour differences in the telescope used, the spectral classes furnish an indication of the colour. Thus O and B stars are bluish white, A and F white, G yellow, K orange and M stars reddish. A good reference work in the historical, general, and mathematical study of double stars is Aitken’s The Binary Stars. † or ††, one or two of the components are themselves very close visual double or, more generally, spectroscopic binaries. By F r a n k S . H ogg

Of the naked eyes stars visible to a northern observer, nearly a hundred are known to undergo variations in their light. With field glasses or a small telescope the number of variables is enormously increased. Thus there is no dearth of material with which an inquisitive amateur may satisfy himself as to the reality and nature of the fluctuations of the light of stars. Further this curiosity may be turned to real scientific value, in that the study of variable stars is one of the best organized and most fruitful fields of research for amateur observers. For years the professional astronomer has entrusted the visual observation of many of the most important variable stars entirely to amateurs, as organized into societies in England in 1890, America in 1911, and France in 1921. The American Association of Variable Star Observers has charts of the fields of 350 of these stars, and in general supervises the work of amateur observers. The Recorder is Mr. Leon Campbell, at the Harvard Observatory, Cambridge, Massachusetts. New observers are welcomed, and supplied with charts. In our galaxy there are already known about 5,000 variables, while in globular clusters and outside systems there are some 3,000 more. Almost all those which have been sufficiently studied may be conveniently classified, according to their light variation into ten groups, by Ludendorff's classification. His classes, with their typical stars, are listed as follows: I. New or temporary stars: Nova Aquilae 3, 1918. II. Nova-like variables: T Pyxidis, RS Ophiuchi. III. R Coronae stars: R Coronae Borealis. Usually at constant maximum, with occasional sharp minima. IV. U Geminorum stars: U Geminorum. Usually at constant minimum, with occasional sharp maxima. V. Mira stars: o Ceti. Range of several magnitudes, fairly regular period of from 100 to 600 days. VI. μ Cephei stars: μ Cephei. Red stars with irregular variations of a few tenths of a magnitude. VII. RV Tauri stars: RV Tauri. Usually a secondary minimum occurs between successive primary minima. VIII. Long period Cepheids: δ Cephei. Regular periods of one to forty-five days. Range about 1.5 magnitudes. IX. Short period Cepheids: RR Lyrae. Regular periods less than one day. Range about a magnitude. X. Eclipsing stars: βPersei. Very regular periods. Variations due to cover­ ing of one star by companion.

1940 maxima of bright variable stars (E.S.T .) o Ceti Jul. 28 β Lyr Jan. 2 .2 , 15.1, etc. δ Cep Jan. 1 .8, 7.2, ecc. R Sct Mar. 8, Jul. 28, Dec. 16 X Cyg Sept. 30 β Per (See pp. 27-4 1) Most of the data in this Table are from Prager’s 1936 Katalog und Ephemeriden Verdnderlicher Sterne. The stars are arranged alphabetically in order of constel­ lations. The second column, the Harvard designation, gives the 1900 position of the star. The first four figures of the designation give the hour and minute of right ascension, the last two the declination in degrees, italicised for stars south of the equator. Thus the position of the fourth star of the list, δ Cephei, is R.A. 22h 25m, Dec. +57 , (222557). The remaining columns give the maximum and minimum magnitudes, spectral class, the period in days and decimals of a day, the classification on Ludendorff’s system, and the discoverer and date. In the case of eclipsing stars, the spectrum is that of the brighter component. The measurement of the distances of the stars is one of the most important problems in astronomy. Without such information it is impossible to form any idea as to the magnitude of our universe or the distribution of the various bodies in it. The parallax of a star is the apparent change of position in the sky which the star would exhibit as one would pass from the sun to the earth at a time when the line joining earth to sun is at right angles to the line drawn to the star; or, more accurately, it is the angle subfended by the semi-major axis of the earth’s orbit when viewed perpendicularly from the star. Knowing the parallax, the distance can be deduced at once. For many years attempts were made to measure stellar parallaxes, but without success. The angle to be measured is so exceedingly small that it was lost in the unavoidable instrumental and other errors of observation. The first satisfactory results were obtained by Bessel, who in 1838, by means of a helio- meter, succeeded in determining the parallax of 61 Cygni, a 6th magnitude star with a proper motion of 5" a year. On account of this large motion the star was thought to be comparatively near to us, and such proved to be the case. At about the same time Henderson, at the Cape of Good Hope, from meridian-circle observations, deduced the parallax of Alpha Centauri to be 0".75. For a long time this was considered to be the nearest of all the stars in the sky, but in 1913 Innes, director of the Union Observatory, Johannesburg, South Africa, discovered a small 11th mag. star, 2° 13' from Alpha Centauri, with a large proper motion and to which, from his measurements, he assigned a parallax of 0".78. Its brightness is only 1/20,000 that of Alpha Centauri. In 1916 Barnard discovered an 11th mag. star in Ophiuchus with a proper motion of 10" per year, the greatest on record, and its parallax is about 0".53. It is believed to be next to Alpha Centauri in distance from us. The distances of the stars are so enormous that a very large unit has to be chosen to express them. The one generally used is the light-year, that is, the distance travelled by light in a year, or 186,000x60x60x24x365¼ miles. A star whose parallax is 1" is distant 3.26 light years; if the parallax is 0".1, the distance is 32.6 l.-y.; if the parallax is 0".27 the distance is 3.26 ÷ .27 = 12 l.-y. In other words, the distance is inversely proportional to the parallax. In recent years the word parsec has been introduced to express the distances of the stars. A star whose distance is 1 parsec is such that its par-allax is 1 sec-ond. Thus 1 parsec is equivalent to 3.26 l.-y., 10 parsecs =32.6 l.-y., etc. In later times much attention has been given to the determination of paral­ laxes, chiefly by means of photography, and now several hundred are known with tolerable accuracy. THE SUN'S NEIGHBOURS

By J. A. P e a r c e Through the kindness of Dr. Adriaan van Maanen, who has supplied the fundamental data, this table has been revised to contain all stars known to be nearer than five parsecs or 16.3 light-years. One star of the former table, has been discarded, and five new members have been added, making a total of forty stars in a space of 524 cubic parsecs. With the exceptions of Sirius, Procyon and Altair, all the stars are dwarfs; the list including the three white dwarfs, Sirius B, 40 Eridani B, and van Maanen's star. Forty-five per cent. of the stars are members of binary systems.

Note.—Magnitudes in brackets are photographic, all others are visual. A colour index of +2.0 has been taken to compute the visual absolute magnitudes of these stars. Symbols: Sp, spectrum; μ , proper motion; π, parallax; L.-y., light- year; m, apparent magnitude; M, absolute magnitude; L, luminosity compared to the sun. THE BRIGHTEST STARS Their Magnitudes, Types, Proper Motions, Distances and Radial Velocities

By W. E. H a r p e r The accompanying table contains the principal facts regarding 259 stars brighter than apparent magnitude 3.51 which it is thought may be of interest to our amateur members. The various columns should be self-explanatory but some comments may be in order. The first column gives the name of the star and if it is preceded by the sign || such means that the star is a visual double and the combined magnitude is entered in the fourth column. Besides the 48 thus indicated there are 12 others on the list with faint companions but for these it is not thought that there is any physical connection. In the case of the 20 stars variable in light this fourth column shows their maximum and minimum magnitudes. The 19 first magni­ tude stars are set up in bold face type. In the fifth column are given the types as revised at various observatories— principally at our own, but omitting the s and n designations descriptive of the line character. The annual proper motion follows in the next column and this may not necessarily be correct to the third decimal place. The parallaxes are taken from the Yale Catalogue of Stellar Parallaxes 1935, the mean of the trigonometric and spectroscopic being adopted. The few nega­ tive trigonometric parallaxes were adjusted by Dyson’s tables before being combined with the spectroscopic. The distance is given also in light years in the eighth column as to the lay mind that seems a fitting unit. The absolute magnitudes in the ninth column are the magnitudes the stars would have if all were at a uniform distance of 32.6 light years (π = 0."1). At that distance the sun would appear as a star of magnitude 4.8. The radial velocities in the last column have been taken from Vol. 18 of the Lick Publications. An asterisk * following the velocity means that such is vari­ able. In these cases the velocity of the system, if known, is given; otherwise a mean velocity for the observations to date is set down. Of the 258 stars or star systems here listed 146 are south and 113 north of the equator. This is to be expected from the fact that the northern half of the sky includes less of the Milky Way than the southern. The number in each spectral class, apart from the one marked peculiar, is as follows: O, 3; B, 74; A, 55; F, 22; G, 43, K, 42 and M, 19. The B-stars are intrinsically luminous and appear in this list out of all proportion to their total number. The stars in Classes A and K are by far the most numerous but the revision of types throws many originally labelled K back into the G group. From the last column we see that 98 velocities are starred, indicating that 38 per cent of the bright stars, or at least one in every three, are binary in char­ acter. For visual binaries the proportion has usually been listed as one in nine. Our list shows one in six but it is only natural to expect that we would observe a higher proportion among the nearby stars, such as these are on the average. Other relationships can be established from the list if our amateur members care to study it.

STAR CLUSTERS AND NEBULAE

Prepared by J. F . H e a r d The amateur who possesses a telescope will find great interest in the observa­ tion and identification of star clusters and nebulae. Such objects, of course, have been extensively catalogued and classified. The most frequently quoted catalogue is Dreyer’s New General Catalogue (N.G.C.) containing 7,840 objects, extended by the Index Catalogue (I.C.) containing 5,386 more. The most interesting catalogue historically, however, and one which is still quoted for reference to the more conspicuous objects is Messier’s Catalogue (M) which contains 103 objects. It was drawn up in 1781 by Charles Messier for his own convenience in identifying comets. Messier’s Catalogue as given below is adapted from a publication by Shapley and Davis (Pub. A.S.P., XXIX, 178, 1917). It includes the Messier number, the N.G.C. number, the 1900 position, the classification of the object and, under remarks, the name of the object (if any). The classification is not that of Messier; it is the new classification based on modern knowledge of these objects. The clusters are classified as open clusters, which are loose irregular aggregates usually of a few scores of stars, or as globular clusters which are compact aggregates of probably hundreds of thousands of stars in spherical formation. The nebulae are classified as diffuse, planetary or spiral. The diffuse nebulae are great clouds of gas and “star-dust” rendered luminous by nearby stars and the planetaries are compact atmospheres of the same materials surrounding a single star. The spirals, on the other hand, are self-luminous and quite outside our stellar system and must be thought of as island universes or other galaxies like our own.

MESSIER’S CATALOGUE OF CLUSTERS AND NEBULAE

R.A. Dec. Messier N.G.C. (1900) (1900) Type of Object Remarks h m ° ' 1 1952 5 28.5 +21 57 Diffuse nebula The Crab nebula in Taurus 2 7089 21 28.3 - 1 16 Globular cluster 3 5272 13 37.6 +28 53 Globular cluster 4 6121 16 17.5 -26 17 Globular cluster 5 5904 15 13.5 + 2 27 Globular cluster 6 6405 17 33.5 -3 2 9 Open cluster 7 6475 17 47.3 -3 4 47 Open cluster 8 6523 17 57.6 -2 4 23 Diffuse nebula The Lagoon nebula —very large 9 6333 17 13.3 -18 25 Globular cluster 10 6254 16 51.9 - 3 57 Globular cluster 11 6705 18 45.7 - 6 23 Open cluster 12 6218 16 42.0 - 1 46 Globular cluster 13 6205 16 38.1 +36 39 Globular cluster The Hercules cluster —best example R.A. Dec. Messier N.G.C. (1900) (1900) Type of Object Remarks R.A. Dec. N.G.C. (1900) (1900) Type of Object RemarksMessier The above map represents the evening sky at Midnight...... Feb. 6 11p.m...... " 21 10 " ...... Mar. 7 9 " ...... " 22 8 " ...... Apr. 6 7 " ...... " 21 The above map represents the evening sky at Midnight...... May 8 11 p.m...... " 24 10 " ...... June 7 9 " ...... “ 22 8 " ...... July 6 The above map represents the evening sky at Midnight...... Aug. 5 11p.m " 21 10 " ...... Sept. 7 9 " ...... " 23 8 " ...... Oct. 10 7 " ...... " 26 6 " ...... Nov. 6 5 " ...... " 21 The above map represents the evening sky at Midnight...... Nov. 6 11p.m...... 21 10 “ ...... Dec. 6

9 “ ...... " 21 8 " ...... Jan. 5 7 " ...... " 20 6 " ...... Feb. 6 BEGINNING OF MORNING AND ENDING OF EVENING TWILIGHT

The above table gives the local mean time of the beginning of morning twilight, and of the ending of evening twilight, for various latitudes. To obtain the corresponding standard time, the method used is the same as for correcting the sunrise and sunset tables, as described on page 10. The entry ------in the above table indicates that at such dates and latitudes, twilight lasts all night. This table, taken from the American Ephemeris, is computed for astronomical twilight, i.e., for the time at which the sun is 108° from the zenith (or 18° below the horizon). TRANSIT OF MERCURY, 1940 NOVEMBER 11-12 A transit of Mercury over the sun’s disk, 1940 November 11-12, is partly visible in Canada. The ingress is visible generally in North America except the northeastern part, South America except the extreme eastern part, the Pacific Ocean, the Antarctic Ocean, Australia, and the extreme northeastern part of Asia. The egress is visible generally in the extreme northwestern part of North America, the Pacific Ocean except the extreme eastern part, Australia, Polynesia, the Antarctic Ocean, the Indian Ocean, and Asia except the extreme western part. The accompanying table gives, for each Time Zone, the Standard Time of ingress for an observer on the standard meridian. In order to find the position of Mercury on the sun’s disk at sunset, using the diagram below, the table gives the times between ingress and sunset for various latitudes. The times for stations not on the standard meridian may be obtained by applying the corrections tabulated on page 10.

The Geocentric Phases of the Transit of Mercury, 1940 November 11-12. The positions of Mercury on the sun’s disk are shown at one-hour intervals from the time of ingress, external contact. T e m p e r a t u r e a n d P recipitation a t C a n a d ia n a n d U n it e d S t a t e s S t a t io n s Prepared by Andrew Thomson.

Mean Temperature, Fahrenheit. Average A nnual. Station. Jan. Feb. Ma. Ap. May Ju. Jul. Aug. Sep. Oc. No. De. M H L

M, H and L are the mean and the averages of the highest and of the lowest temperatures each year at the station, over the total time since the station was installed.

Mean Precipitation. (Unit = one tenth of an inch) Year. Station Jan. Feb. Ma. Ap. May Ju. Jul. Aug. Sep. Oc. No. De. M W D

M, W and D indicate the mean, the greatest and the least total precipitation in one year from Jan. 1 to Dec. 31 recorded at a station, records being available for varying periods from 30 to 50 years. THE ROYAL ASTRONOMICAL SOCIETY OF CANADA 1890-1940 This year marks the completion of the first fifty years of the corporate existence of our Society. The Society was incorporated in 1890 under the name of The Astronomical and Physical Society of Toronto, and assumed its present name in 1903. For many years the Toronto organization existed alone, but now the Society is national in extent, having active Centres in Montreal, P.Q .; Ottawa, Toronto, Hamilton and London, O nt.; Winnipeg, M an.; Edmonton, A lta.; Vancouver and Victoria, B.C. As well as about 700 members of these Canadian Centres, there are over 200 members not attached to any Centre, mostly resident in other nations, while some 300 additional institutions or persons are on the regular mailing list for our publications. The Society publishes a monthly J o u r n a l containing about 500 pages and a yearly Observer's Handbook of 80 pages. Single copies of the J o u r n a l or H a n d b o o k are 25 cents, postpaid. In quantities of 10 or more copies, the price is 20 cents a copy. Membership is open to anyone interested in astronomy. Annual dues, $2.00; life membership, $25.00. Publications are sent free to all members or may be subscribed for separately. Applications for membership or publications may be made to the General Secretary, 198 College St., Toronto.

The year 1940 also marks the hundredth anniversary of the founding in Toronto of the first Observatory (magnetic) in Canada. This was one of the first magnetic observatories in the world and became the nucleus of observatory development in Canada. To mark the semi-centennial of the founding of our Society and the cen­ tenary of the founding of the first observatory, our Society plans to hold a special meeting in Toronto in the late summer. It is also planned to publish as a feature of the J o u r n a l, articles and early documents dealing with the histories of the observatory and of the society.

The Society has for Sale: Reprinted from the J o u r n a l of the Royal Astronomical Society, 1936-1939. The Physical State of the Upper Atmosphere, by B. Haurwitz, 96 pages; Price 50 cents postpaid. The Small Observatory and its Design, by H. Boyd Brydon, 48 pages; Price 25 cents postpaid. General Instructions for Meteor Observing, by Peter M. Millman, 18 pages; Price 10 cents postpaid. Two Inexpensive Drives for Small Telescopes, by H. Boyd Brydon, 12 pages; Price 10 cents postpaid. A. H. Young’s Simple Mounting for the 6-inch Reflector, by H. Boyd Brydon, 16 pages; Price 10 cents postpaid.

Send Money Order to 198 College St., Toronto.